Effects of substrate on cracking patterns and dynamics in desiccating clay layers

Abstract

Desiccation cracking is ubiquitous in many materials of practical importance, such as in mud, clay soil, pavement, and concrete, and understanding its dynamics and formation is essential for developing an effective means of its prevention or utilization. We report on a phenomenological investigation aimed at delineating the effect of a coarse-textured substrate on the cracking dynamics and morphology of an overlying kaolinite clay layer. Drying experiments were carried out using a glass container mounted on a digital balance, packed with a thin layer of kaolinite clay overlying seven types of sand that differed in their particle size distributions. An automatic imaging system recorded the dynamics of cracking at the evaporating surface. Dynamic analysis suggests a decreased duration of cracking with increased substrate particle size and substrate-independent initial crack propagation. Analysis of the cracking morphology indicates a decreased crack density and larger crack length, and an increased crack width mean and standard deviation with increased substrate particle size. Scanning electron microscopy results, used to study the extent of cracking over various length scales, indicate that only macroscopic cracks formed on the kaolinite clay surface. Fractal and density correlation function analysis of the final crack networks indicate the dependency of the fractal dimension on the substrate particle size, and a crossover length scale n that separates the fractal regime from the uniform crack density regime. For length scales greater than n, the density correlation function asymptotically approaches the crack density at the surface of the clay.

The role of rock fragments in crack and soil structure development: a laboratory experiment with a Vertisol

“…The trends in mean width, standard deviation and skeleton density (Table ) demonstrate that the surface crack network became narrower, with more homogeneous crack widths, and more complex as the size of rock fragments decreased and as their content increased. The same trends that we found for mean width and skeleton density with respect to RF size were also observed by DeCarlo & Shokri () with respect to the particle size of coarse‐textured substrate that they placed below thin clay layers. The increase in crack or pore area with RF content, coupled with the decrease in mean width, can be explained by a change in the crack or pore size distribution resulting from RF addition.…”

Morphometric analysis of polygonal cracking patterns in desiccated starch slurries

“…At the initial stage (47 min after the start of drying), long primary cracks appeared one-by-one, breaking the slurry surface in a sequential manner into several domains. Every two connected primary cracks showed an almost vertical intersection, as in the agreement with earlier studies on various kinds of water-grain mixtures [24][25][26][27] . It is known that the spacing between primary cracks occurring on the dried corn starch surface is several times larger than the starch layer thickness.…”

“…Earlier studies have elucidated the mechanism of desiccation crack formation for various grain-liquid mixtures [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] . The mixtures typically consist of a skeleton of solid grains and pore spaces that are filled with either liquid or air bubbles.…”

Patterns of Desiccation Cracks in Saline Bentonite Layers

“…The above justification is consistent with the results observed in Fig. 6 as well as the data reported in DeCarlo and Shokri (2014a).…”

“…More recently, Kamai et al (2009) investigated the evaporation process from surface-exposed fractures and illustrated how the drying process is significantly modified as a result of the presence of fractures. The importance of the presence of cracks in clayey soil and its hydrological consequences motivated many scientists to investigate cracking patterns and dynamics under a variety of boundary conditions (e.g., Newson 2001, 2005;Tang et al 2010Tang et al , 2011Trabelsi et al 2012;Sanchez et al 2013;DeCarlo and Shokri 2014a;Thiery et al 2015). Hallett and Newson (2005) investigated how the soil clay content and pore water salinity influenced the ductile fracture mechanics of soil.…”